Heterodyne oscillator



Jan. 24, 1933. PORTS 1,895,103

HETERODYNE OSCILLATOR Filed March 7, 1951 IYNVENTOR EARL c. PORTSATTORNEY Patented Jan. 24, 1933 UNITED STATES EARL G. PORTS, FWOODSIDCE, NEW YORK,

PATENT OFFICE ASSIGNOR 'IO INTERNATIONAL OOMMUNI- CA'I'IONSLABORATORIES, INC., 013 NEW YORK, N. Y., A CORPORATION OF NEW YORKHETERODYN E OSCILLATOR Application filed March 7,

' systems and more particularly to systems v 3.5 ductances and 6 andtuning condenser adapted to receive signals of either damped or undampedoscillations. v It is one of the objects of this invention to provideareceiving system which, for one adjustment, will act as a regenerativeamplifier system and, for another adjustment, will be adapted forheterodyne reception.

-Another object isto provide a frequency selecting network whereinadjustment of a single tuning elementina frequency selecting circuiteffects tuning control of a second circuit inductively-coupled to theselecting circuit, and a third circuit, which is both in? ductively andconductively coupled to the said frequency selecting network. I

These objects, and certain novel features of the invention, will bepointed, out with greater particularity in the appended claims. For amore complete understanding of my invention, reference may be had to thefollowing description taken in connection with the accompanying drawing.7

As shown in the drawing, I provide an antenna 1, the periodicity ofwhich may be determined by adjustment of condenser 2 r in thetunedantenna circuit 23. Signals of radio frequency picked up by antenna 1traverse the antenna tuned circuit 2-,3. Variable coupling 4 havingprimary 3 and secondary '5 servesto transfer energy from antenna 1 to afrequency selecting network comprising? in- 8 is a connection fromcircuit 5.67 to common ground lead 9. Connection 8 may containcondenser--18 as hereinafter explained. Coupling 10, comprising coils6-11-12, is so arranged that the inductance coil 6 of the tunedfrequency selecting circuit 56--7 has an external field capable ofproviding sufficient coupling through coils 11 and 12 to determine,electrically, the frequency of the units associated with coils 11 and12.

The electron discharge device 13 having filament 14, grid. 15 and plate16 is of the wellknown type and isadapted to act as an oscillatororregenerative amplifier by controlling plate feed-back connection 17 bymeans of condenser 18. A source of voltage 19 is con- 1931. serial No.520,783.

nected to plate 16 through radio frequency choke 20. Althoughcondenser18 is shown in its preferred position in lead 17, it ispossible to have the regeneration'control connected to the tunedselecting circuit 567 through connection 8 to ground 9, as shown by thedotted lines in the figure, in which case, condenser 18 in the platefeed-back would be replaced by a conductive connection. I find, however,that with the condenser in its preferred position, regeneration is moreeasily controlled at the higher frequencies by eliminating the effect ofmutual and distributed capacities incident to the actual construction ofcoils 6, l1 and 12;

Detector 21 is preferably of the thermionic type'and comprises'controlelectrode 22, filament 23 and plate 245as shown. A telephone or signalrecording device 25 having by-pas's condenser 26 associated therewith isconnected in circuit with detector plate24; Source 27 supplies energy todevice 25. It is, of course, understood that any number of stages ofaudio amplification, not shown, may be placed intermediate the detector21 and signal recording device 25.

By adjustment of condenser 18 to a point just below the pointofoscillation, tube 13 will act as a regenerative'amplifierfor radiofrequency oscillations, the frequency of the amplified currents inducedin coil 11 through inductance 6 being controlled, by reason of closecoupling 10 of coils 61112, by adjustment of condenser 7 in the tunedfrequency selecting circuit 5-6-7.

For the reception of continuous (undamped) wave signals, by theheterodyne principle, the value of condenser 18 must be increased to thepoint where oscillation has just commenced, in which case the frequencyof the oscillator 13 would be governed by the frequegcy of the timedselecting circuit 56 Incoming signals will be passed on to coil 11 andthence to the grid 22 of detector 21 along with the locally generatedoscillations, and in the detector 21 the resulting beat or differencefrequency will'causecurrent of audio frequency to flow through thefollowing amplifier or telephone receiver.

Thus, no tuning'condenser is necessary directly in grid of the detector,since tuning is accomplished in the frequency selecting network incircuit with the plate circuit of the oscillator.

Since the frequency of the local oscillator must differ from thefrequency of the incoming signal by an amount corresponding to an audiofrequency, it is necessary to slightly detune circuit 5 67. The detuningnecessary for heat reception is not sufiicient to reduce, materially,the amplitude of. the

incoming waves, and byvirtue of the heteroall of said inductancesv.loeing coupled together, and a variable condenser, in circuit withsaid first output circuit and said frequency selecting networkforcontrolling the operation of said electron discharge device.

2. In a radio receiving system adapted to receive signals of eitherdamped or undamped waves, an electron discharge device having input andoutput electrodes, a tuned frequency selecting network having an outputcircuit, a. feed-back connection between said output electrode and saidfrequency selecting network, a detector having an input circuit,inductances individual tosaid input electrode andsaid input circuit, andan inductance commonto said output electrode and said output circuit,allof said induc tances being coupled together, and means for controllingthe amount of energy in said feedback connection.

3. An arrangement as claimed in claim 2,

characterized in'that, said means is a condenser, includedserially insaid feed-back connection. V

. 4; An arran ement as claimed in claim 2,

characterized in that, the said meansis a condenser having one terminalconnected to said frequency selecting network, and the other connectedto the output electrode of the said'electron discharge device.

5. A radioreceiving system adapted to receive signals of either dampedor undamped waves, comprising an antenna, a tuned frequency selectingcircuit. having afirst and a second inductance, said first inductancebeingcoupled to said antenna, a detector having "an input inductance, anelectron discharge device having an input inductance and an outputcircuit inductance, saidoutput circuit, a detector having an inductancein inductance and said second inductance being common to said frequencyselecting circuit and said output circuit, means for coupling saidcommon inductance and said'input inductances together, means forproducing oscillations in all of said inductances,-means in said,frequency selecting network for controlling'the frequency ofsaidoscillations, and avariable condenser in electrical asso:ciationwith said output circuit and said frequency selecting'circuitforcontrolling regeneration in said electron discharge device. I c

6. -In a radio receiving system adapted to receive signals of eitherdamped or undamped -waves, an-electron discharge device having input andoutputcircuits, a tuned frequency selecting network having an outputcircuit,

a detector having an input circuit, inductancesindividual to: each ofsaid input circuits, an inductance common to said output circuits, 'allof saidinductances being con pled together, means for producing oscillations in all of said inductances, and atan able condenser in saidfrequency selecting network for controlling the frequency of saidoscillations. w I I '7. 'In' a radio receiving system adapted to receivesignals of either damped or und'amped waves, anelectron discharge devicehaving input and output circuits, a tunedfr'equency selectingnetworkhaving an output circuit,

ta'nces' individual to each of said inputcircuits, all of saidinductances being coupled together,and variable means in circuit with hsaid first output circuit and said "frequency selecting network forcontrolling theoperation of said electron discharge'device.

j 8. Thecombination in a radio receiving system, of an antenna, circuitincluding an inductance, a tuned frequency selecting circuit comprisinga first and a second inductance, the said first inductance beininductively coupled to said antenna in uctance, an electron dischargedevice having input and output circuits, a detector having-an inputcircuit, inductive means'coupling said inductance. and said inputcircuits, and a connection from said output circuit to said I tunedfrequencyselecting, circuit.

9. The combination in a radio receiving system, of atuned antennacircuit including an inductance, a tuned frequency selecting circuitcomprising a first and second induca detector having an input circuit,induc-i tance, the said first inductance being induc v tivelyjcoupledto'said antenna inductance, an electron discharge device-havinginput and output circuits, an inductance in said 7 input its inputcircuit, said secondinductance .in i

said tuned frequencyselecting circuit and the inductances in' said'input circuits of the electron discharge device and of said detectorbeing inductively coupled together, and a no connection from said outputcircuit of said discharge device to said tuned frequency selootingcircuit.

In Witness whereof, I hereunto subscribe my name this 6th day of March,1931.

EARL G. PORTS.

